Direct-write/read electron-beam lithography of semiconductor device circuit patterns on a semiconductor target wafer in the fabrication of microcircuit devices offers a number of advantages over photon beam (optical or x-rays) methods. These advantages include more accurate edge placement and pattern overlay, elimination of the need for masks or reticles, and higher resolution. However, known electron-beam lithography machines employing a single electron beam are at least 5 to 10 times slower than current optical exposure stations, basically because of the serial nature of the known electron-beam lithography exposure techniques compared with the parallel nature of optical exposure of the semiconductor device circuit patterns through a mask or reticle. Therefore an electron-beam lithography system and method is needed which exposes more than a single location serially of a semiconductor circuit pattern by direct electron beam writing.
A multi-channel electron-beam lithography system previously has been described in U.S. Pat. No. 4,390,789 issued June 28, 1983 to Donald O. Smith and Kenneth J. Harte for an "Electron Beam Array Lithography System". This known patented system employs a plurality of individually controlled double-deflection electron beam optical columns (also known as a compound, or fly's eye, or matrix lens optical column). In this known system the electron beam in each column is first deflected by a coarse deflector to a single selected fine (fly's eye) lens and fine deflector sub-assembly with each such fine lens and fine deflector sub-assembly being serially accessed by the electron beam via the coarse deflector. The double deflection system thus comprised is relatively low in current density, complex in construction, expensive and has the additional disadvantage of producing a beam with a relatively large angle from the normal to the wafer surface at the edges of the fine deflection fields.